The distribution of inorganic phosphate ions in body fluids is calculated by equilibrium studies. Equations of partial mol fractions of each complex species are calculated with known stability constants, measured pH and electrolyte concentrations. We present these results in serum and urine in health, and in some diseases, with characteristic pH values and electrolyte concentrations. Distribution of various inorganic phosphate complexes, similar to total and ionized calcium, may be of practical importance.